Analysis Cause of Main Engine Failure The main engine failure started with the No3 con-rod bottom end detaching from the crankshaft. This triggered a chain of parts separation. With no cap to hold it in place, the con-rod unseated from the crank pin and struck the counterweight. The impact sheared the pin securing the counterweight in its notches. As the crankshaft continued to rotate, it struck the counterweight and con-rod, jamming them against the lower edge of the No3 cylinder liner. The force transmitted by the con-rod top end to its gudgeon pin caused the piston skirt to break into several pieces. The impact of the con-rod bottom end striking the starboard casing wall punctured the casing, damaging the oil and fresh water lines. In most cases of con-rod detachment, the bottom end cap separates from the upper part of the con-rod, which is caused by a failure of either the securing bolt or the cap. The bolts usually fail in fatigue caused by unequal torquing. Photo 4. Surface of crack in con-rod cap. Note the fatigue striations covering over 95 percent of the surface. The letter O marks the point of origin of the crack, and D indicates the bearing shell contact surface The Board determined that the con-rod cap became detached from the con-rod due to a fracture and not due to failure of the bolts. It was noted that the crack developed in the thinnest section of the con-rod cap.7 It originated in a corrosion pit on the contact surface with the bearing shell, then propagated to over 95percent of the cap surface through high cycle fatigue. The cap subsequently failed in overload in the smallest section. The break-up of the cap caused the four bolts to fracture. In this occurrence, the con-rod cap fractured near its centre. This seldom occurs, since the central portion is generally subjected to very little stress. Stresses are normally concentrated in the upper portion of the con-rod. Equipment Maintenance Role of Manufacturer Each manufacturer builds its engines to specific manufacturing standards, which vary considerably throughout the range of products available on the market. All new marine engines come with a warranty against manufacturing defects. To maintain original performance, the use of original parts is highly recommended, coupled with operating instructions and maintenance schedules provided by the manufacturer. For instance, SEMT Pielstick prescribes that connecting rods be inspected regularly8 and recommends that a dye penetration test be conducted on the serrated area after 24,000running hours, because of its susceptibility to cracks. Subsequent to this occurrence, TSB analysis on the connecting rod cap revealed that cracks were present in this serrated area, illustrating the importance of following manufacturer's recommended maintenance practices. Photo 5. TSB Engineering Laboratory conducted a dye penetration test on the serrated area of the damaged con-rod cap. Cracking is clearly visible. Owner Responsibility Owners generally maintain a vessel in a seaworthy condition by complying with IMO conventions adopted by the flag state and implemented by regulation and with rules and standards of the ship's classification society. Most ship's engines are maintained in accordance with maintenance programs recommended by the manufacturer. Engine performance and service life depend mainly on maintenance and the owner's commitment to follow manufacturer recommendations. Any major repairs carried out at sea should be reported to the classification society. This was not done in August1999. The manufacturer of the main engine of the MilleniumYama recommended a stringent inspection after a specific period of operation. On an ocean-going vessel of this type, the main engine may run 6,000to 8,000hours a year, depending on the type and number of voyages made. It is estimated that all of this main engine's parts were inspected at least four times. The ship's maintenance log indicates that all 12units of the main engine were overhauled since it was purchased in 1998. Role of Classification Society Classification societies dictate how ships are built and maintained. Surveys are undertaken at regular intervals to ensure that the condition of a ship and it's machinery satisfies the requirements of classification rules. The MilleniumYama was monitored by ABS, a member society of the International Association of Classification Societies (IACS). The society has observer status at IMO, and its principal objectives are to ensure maximum safety at sea and to prevent marine pollution. Engine room components essential to vessel operation are monitored. Critical parts of the main engine must be meticulously inspected. However, only the parts that are actually in the engine are inspected. All new parts are approved by the classification society, but parts that are used but considered to be still good are not inspected, unless they undergo repairs or a major modification. Generally, societies have no system for identifying condemned parts. As such, if a condemned part is not destroyed or identified, it can be reinstalled on board or on another engine. Quality Control of Parts The main engine had sustained major damage several times since the ship was launched in 1979. The damage forced the owners to replace several major parts, including the crankshaft, cylinder head, con-rods, pistons (crown and skirt), gudgeon pins, main bearing shells, and liners. Parts, like pistons, cylinder heads, con-rods, injectors, starting air valves, relief valves, and inlet/exhaust valves, are often replaced with used parts that meet manufacturer specifications. On some vessels, large parts, like pistons, con-rods, cylinder heads, and head components, are pre-assembled to facilitate replacement and reduce repair time. This practice can result in inadequate parts control. After several replacements, parts are interchanged with others in the main engine; parts in a given unit no longer bear the same number as the unit. It is possible that the con-rod marked No11 was present when the crankshaft was previously damaged. It may have been damaged at that time, removed from the engine, and kept on board as a spare. Then, when emergency repairs were done at sea in August1999, it would have been installed in the No3 unit. No documentation was found to indicate that spare parts were certified valid and within specification when the vessel was sold in 1998. Since the last change of ownership, engine room personnel had to rely on their own experience, due to a lack of information, to judge the quality of replacement parts in the main engine. Ship Documentation Regulation 2, Chapter IX of the 1974 International Convention for the Safety of Life at Sea (SOLAS), adopted in 1994, states the application date of the ISM Code for general cargo vessels as being not later than 1July2002. The owner had already begun to forward to the vessel reference documentation required to comply with the ISM Code. One chapter covers machinery maintenance, parts inventory, and quality control. The main engine and generators are major components. The main engine provides propulsion power and, in many cases, contributes to keeping the vessel seaworthy in foul weather. The generators produce electrical power required to operate all on-board equipment. Modern machinery, propulsion machinery in particular, is increasingly sophisticated and sometimes operates close to its performance limits. The condition of machinery parts is critical to maintaining that level of performance and, therefore, they require meticulous maintenance. To maintain optimum performance, each part should receive individual attention. When a component repeatedly exhibits diminished performance or frequently breaks down, the person in charge records these events in a log, which is useful for all engine room personnel and can assist in evaluating the condition of an engine. Reference documentation is specific to each company and may vary according to the type of vessel. This documentation is indispensable for determining machinery performance and engine room effectiveness. Since engine room logs belong to the owners of a vessel, very little historical information on the defective connecting rod could be obtained. The only information found was its number (11), the approval number (A404B),9 and the date of manufacture (1977). Record Keeping and Documentation This occurrence took place in a relatively unrestricted waterway. It could equally have occurred in confined waters, however, where the consequences might have been more serious. One of the advantages of the ISM Code is that it requires that information be documented. In the shipping industry, a great deal of information concerning the main engine and other components is conveyed verbally. Although this form of communication is very common, it is not adequate in all situations, particularly in situations where there are changes in personnel, There is a strong possibility that information will be altered, misinterpreted, or lost. Many changes relating to risk management are currently under way in the shipping industry: In July 1995, the IACS implemented the Transfer of Class Agreement (TOCA) to eliminate the possibility that required repairs would not be made after a change of classification society and to ensure through life compliance. As of 1 January 1996, for PSC, an enhanced survey program has been in effect for bulk carriers and oil tankers of at least 500grosstons.10 The program concerns inspections of the ship's structure and inspection program documentation, which must be kept on board throughout the life of the vessel. Safety is enhanced when the history of a vessel and its equipment is available. The MilleniumYama has changed ownership five times. The lack of information on its replacement parts history is due to relevant information not being passed on from previous owners to subsequent owners. There are no regulations requiring owners to have and maintain on-board records of service and replacement parts. Findings as to Causes and Contributing Factors The connecting rod cap detached from the connecting rod due to a fracture that developed in the thinnest section near its centre. No reference documentation was found on board that would have allowed engine room personnel to determine the condition and origin of the connecting rod. Findings as to Risk Classification societies are not required to identify condemned parts. Vessels are not required to have or maintain permanent on-board records of replacement parts, and existing rules and regulations do not address the history of, or quality control for, major parts. Others Findings Major repairs were carried out at sea and not reported to the classification society in accordance with classification rules. Safety Action Action Taken On 7 August 2001, a Marine Safety Information letter was sent to the vessel owners, which summarized the cause of the machinery failure. It advised that there were neither maintenance records aboard nor a system in place whereby records are passed from a current owner to a subsequent one. Such a situation resulted in a new owner having insufficient machinery history data available in order to make informed maintenance decisions and ensure continued safety. In response, the owners of the vessel at the time of the occurrence agreed that the transfer of maintenance records to subsequent vessel owners of the vessel would be advantageous for the purposes of preventative maintenance. It was indicated that the transfer of such records for the MilleniumYama was far from common during the major part of the lifetime of the vessel. However, the owners were fortunate that the vessel had been maintained with the same Classification Society throughout its life and there was, as a result, a contiguous record of all significant maintenance and repair records for the vessel. Having a vessel classed with the same Classification Society throughout it's life will result in continuity of records, however it is only recently that Classification Societies have begun allowing new owners to access historical survey information through online database systems such as Lloyd's Class Direct Online and American Bureau of Shipping's Safe Ship program. However throughout most of the MilleniumYama's service life, such online services had not yet been developed and Classification Societies did not readily release information when a vessel changed hands, especially when accompanied by a change in Class. A copy of the MSI was forwarded to Transport Canada, who responded that they have added the vessel to its Ships of Particular Interest list. As a result, the vessel will be boarded when it arrives in Canada for a Port State Control inspection.